Crawling is the process performed by search engine crawler, when searching for relevant websites on the index. For instance,Google is constantly sending out "spiders" or "bots" which is a search engine's automatic navigator to discover which websites contain the most relevant information related to certain keywords.

Crawling basically means following a path. In the SEO world, crawling means following your links and "crawling" around your website. When bots come to your website And any pages, they follow other linked pages also on your website.

Google's Spider/Crawlers visit web pages to find the information. These crawlers will crawl all webpages and follow links on those pages. They go to each follow link like we do in order to gather the information and they bring data to Google's server about those webpages.